Hindered tris(meta-hydroxybenzyl)cyanurate antioxidants

ABSTRACT

WHEREIN R is a branched chain alkyl group containing three to about 12 carbon atoms are provided. These compounds are useful as antioxidants in organic substrates, such as polyolefins, rubber, etc. They can be prepared by reacting 3 moles of 4-alkyl-3hydroxy-2,6-dimethylbenzyl chloride with 1 mole of cyanuric acid.   Compounds of the formula:

United States Patent mi I 1 Mar. 27, 1973 [54] HINDERED TRIS(META-HYDROXYBENZYL)CYANURATE ANTIOXIDANTS [75] Inventor: Peter Vincent Susi,Middlesex, NJ.

[73] Assignee: American Cyanamid Company,

Stamford, Conn.

22 Filed: Nov. 16, 1971 21 Appl. No.: 199,340

[52] (1.8. Cl. ..260/248 NS, 260/45.8, 252/515 R,

252/403, 99/163 [51] Int. Cl. ..C07d 55/38 [58] Field of Search..260/248 NS [56] References Cited UNITED STATES PATENTS 3,531,483Gilles ..260/248 Primary Examiner-John M. Ford Attorney-Philip Mintzwherein R is a branched chain alkyl group containing three to about 12carbon atoms are provided. These compounds are useful as antioxidants inorganic substrates, such as polyolefins, rubber, etc. They can beprepared by reacting 3 moles of 4-alkyl-3-hydroxy- 2,6-dimethylbenzylchloride with 1 mole of cyanuric acid.

2 Claims, No Drawings HINDERED TRIS(META- HYDROXYBENZYL)CYANURATEANTIOXIDANTS This invention relates to novel compounds useful forinhibiting oxidative degradation of organic materials. Moreparticularly, it relates to compounds of the formula:

on (Inn (in on It CllgN N-cin- R din (an (EH.

CH3- -CH3 wherein R is a branched chain alkyl group containing three toabout 12 carbon atoms. This invention also relates to the use of suchcompounds to inhibit oxidative degradation of organic materials subjectthereto.

It is well known that numerous organic materials tend to deteriorateupon exposure to oxygen in air. Among such materials are polyolefins,ABS resins, polyamides, polyacetals, polystyrene, impact polystyrene,natural and synthetic rubbers including ethylene-propylene copolymersand carboxylated latices, fats, oils, greases, gasoline, etc. It is alsowell known to incorporate various additives (antioxidants) into suchmaterials to inhibit oxidative degradation thereof. This inventionarises out of the continuing search for new compounds which will besuperior antioxidants for such materials.

The present invention is based on the discovery that these novelcompounds, as defined in the above formula, in addition to inhibitingoxidation of organic materials, such as those mentioned above, possessoutstanding resistance to extraction by boiling water, a property whichhas considerable importance when used in plastic materials inapplications such as fibers, washing machine agitators, dish washerparts, and the like, where contact with hot water is likely. Inaddition, these compounds are useful processing antioxidants forpolyolefins; that is, they protect the polymer against breakdown duringmilling, extrusion, and other hightemperature processing operations.

In the compounds of the present invention, the three nitrogens of thecyanuric acid are each connected to a hindered phenolic moiety through amethylene group. It will be noted that the hydroxyl group of eachphenolic moiety is positioned meta with respect to the methylene groupattaching the phenolic moiety to the cyanuric acid. It is criticallyimportant that this hydroxyl group be located in the meta position toavoid discoloration of the substrate in which these compounds are usedand to provide a high degree of antioxidant protection to the substrate.It will also be noted that all positions ortho and para to the hydroxylgroup are substituted, one ortho position with a branched chain alkylgroup and the other two such positions with methyl groups. Thus, thisphenolic moiety is hindered by the branched chain alkyl substituentadjacent to the hydroxyl group.

Illustrative of the branched chain alkyl groups represented by R in theposition ortho to the phenolic hydroxy group in the compounds of thisinvention are isopropyl, t-butyl, secbutyl, t-amyl, sec-heptyl,sec-octyl, t-octyl, t-nonyl (1,1-dimethylheptyl), cr,a-dimethylbenzyl,methylcyclopentyl, methyl cyclohexyl, and the like.

These compounds are readily prepared by known procedures, such as thereaction of one mole of cyanuric acid with three moles of an appropriate4-alkyl-3- hydroxy-2,o-dimethylbenzyl chloride. The benzyl chlorideutilized can be prepared from the corresponding2,4-dimethyl-6-alkylphenol by introducing the chloromethyl group intothe 3-position by reaction with hydrochloric acid and formaldehyde or byreaction with methylal in the presence of hydrochloricacid and sulfuricacid according to the procedure of R. Wegler and E. Regel, Makromol.Chem. 9, l (1952).

These compounds (1) are non-discoloring, (2) exhibit a high degree ofantioxidant protection to the substrate, (3) are resistant to hot waterextraction from the substrate, and (4) afford a high degree of stabilityto the substrate during mechanical processing, and are especially usefulfor inhibiting oxidative degradation of organic materials normallysubject to deterioration upon exposure to oxygen, such as thosementioned above. These compounds may be incorporated into the variousorganic materials to be protected by any of the standard techniques,including stirring, milling, screw extruding, Banbury mixing, swelling,etc. These compounds are effective over a wide concentration range ofabout 0.01 to about 5.0 percent based on weight of material to beprotected. ln polypropylene, a preferred use, they are preferably usedat a concentration between 0.05 and 1.0 percent based on weight ofpolyolefin. After incorporating these compounds into polymericmaterials, during which other ingredients such as fillers, plasticizers,pigments, light absorbers, etc. may be added, the polymer composition isformed into useful shapes by molding, casting, spinning, extrudinginjection molding, or other shaping procedures. In polypropylene, theantioxidant activity of these compounds can be greatly enhanced byconcurrent use therein of esters of thiodipropionic acid, such asdilauryl and distearyl thiodipropionate.

Oxidative deterioration of polypropylene and other similar oxidizableplastic materials is evident from the embrittlement which occurs onexposure to atmospheric oxygen. The extent to which the antioxidantprotects against deterioration is measured in an accelerated test bydetermining the hours to embrittlement at l40-l50 C. when a specimencontaining the antioxidant is exposed in a forced draft oven at thistempera ture.

Extractability of the antioxidant from the plastic by hot water isdetermined by refluxing compression molded films containing theantioxidant in water for a predetermined period of time and then agingthe specimens in a forced-draft oven as described above.

The effectiveness of these compounds as processing antioxidants isdetermined by measuring the melt-index of the polymer containing thecompound after repeated extrusions. The melt index is a measure of themelt viscosity which in turn is related to the molecular weight. Anincrease in the melt index on extrusion indicates a decrease inviscosity and a decrease in molecular weight (processing breakdown). Apolymer blend of unstabilized polypropylene containing 0.1 percent ofthe compound and 0.25 percent distearylthiodipropionate (STDP) isextruded at 460 F. through a 3/4 inch extruder and pelletized. Thepellets are reextruded for a total of four passes. The melt index of thepelletized polymer sample is measured after each pass, according to ASTMmethod D-l238. (STDP is normally incorporated into polypropylene toimprove the long-term aging properties of phenolic antioxidants ingeneral. The contribution of STDP to processing stability is minimal.)

The invention is more fully described in the following illustrativeexamples.

EXAMPLE 1 l ,3 ,5-Tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)-striazine2,4,6( 1H, 3H, 5H)-trione To a stirred mixture of 3.23 grams(0.025 mole) of cyanuric acid and 16.9 grams (0.075 mole) of4-tbutyl-3-hydroxy2,6-dimethylbenzyl chloride in 50 ml.dimethylformamide at 40 C. was added dropwise 12 ml. (0.08 mole) oftriethylamine. The reaction mixture was stirred for 18 hours; 50 ml.water and 50 ml. benzene were added and the two liquid layers separated.The benzene phase was washed twice with 50 ml. portions of water, theremaining water azeotropically removed, and the benzene solutionclarified with 50 g. Superfiltrol. The benzene was removed and replacedwith 50 ml. methanol. After decolorizing with grams of activatedcharcoal and cooling there was obtained 12 grams (78 percent) of theabove identified product, m.p. 150 C. Recrystallization from methanolgave an analytical sample melting at l54-155 C.

Compounds prepared in a similar way include: 1,3,5-Tris(4-sec.butyl-3-hydroxy-2,6-dimethylbenzyl)-striazine-2,4,6( 1H, 3H,5H)trione; l,3,5-Tris(4-isopropyl-3-hydroxy-2,fi-dimethylbenzyl)-s-triazine- 2,4,6(ll-l, 3H,5H)trione; l,3,5-Tris(4-tert. amyl-3-hydroxy-2,6-dimethylbenzyl)-s-triazine-2,4,6(1H, 3H, 5H )trione; 1 ,3,5-Tris(4-t.octyl-3-hydroxy-2,6- dimethylbenzyl)-s-triazine-2,4,6(1H,3H, 5H)trione; l ,3 ,5,-Tris(4-tert.dodecyl-3-hydroxy2,6-dimethylbenzyl)-s-triazine-2,4,6(1H,3H, 5H)trione, and the like.

EXAMPLE 2 Evaluation in Polypropylene The compound of Example 1 wasincorporated into Avisun unstabilized polypropylene at the designatedconcentration by milling at 170180 C. on a standard two-roll laboratorymill. The milled sample was compression-molded into films 15 mil inthickness. Similar films were prepared containing the closest prior artcompound: 1 ,3 ,5-tris( 3,5-di-t-butyl-4-hydroxybenzyl)-s-triazine-2,4,6(1H, 3H, 5H)trione, disclosed in US. Pat. No. 3,531,483,issued Sept. 29, 1970. This prior art compound, which will be identifiedas control compound, has the structure:

The films were aged in a forced-draft oven at 140 C. and the time(hours) to embrittlement recorded (Table I).

Compression molded films containing the antioxidants were refluxed in200 ml. water for 7 hours (1 cycle). The water was replaced at the endof each cycle until 15 cycles hours) of boiling water extractions werecompleted. The films were then aged as above at 150 C. in a forced-draftoven and hours to embrittlement noted (Table l). The oven-aged stabilityof the films after boiling water treatment is a measure of theextractability of the antioxidants.

Table I Compound Made Control No Additive (used at 0.2% in Example 1Comp. Add. concentration) Oven-aging at C Hours to Embrittlement 970-980360-370 4 Oven-aging at C after 15 cycles boiling water 2l5255 23-39Hours to Embrittlement This data shows that the compound of thisinvention is much superior in antioxidant activity as compared to thecontrol compound. Of particular significance is the startling resistanceto extraction by hot water, a most important property with respect tomaterials which are laundered or used immersed in water.

EXAMPLE 3 Processing Properties of Antioxidants in Polypropylene Samplesof unstabilized polypropylene containing 0.1 percent of the compound ofExample 1 and 0.25 percent STDP were compared with samples containing0.1 percent of the control compound of Example 2 and 0.25 percent STDPwith respect to melt index as described herein above. The data are shownin Table II.

Table 11 Melt index (ASTM-D4238) No. of Extrusions Compound of Exam. 1Control Compound The data show that the melt index of polypropylenecontaining the compound of this invention increased only 3 units after 4passes through the extruder whereas the control compound showed anincrease of 7.4 units. This indicates that the compound of thisinvention is superior to the control compound in protecting 6polypropylene against polymer breakdown during wherein R is a branchedchain alkyl containing three to processing. about twelve carbon atoms.

Iclaim: 2. A compound as defined in claim 1 wherein R is 1. A compoundof the formula: tertiary butyl.

O 5 a: OH (3H3 H CH3 ?H R- CHZN NCH R V l 0- on mu CH2, CH9

2. A compound as defined in claim 1 wherein R is tertiary butyl. 